How to customize M3U8 headers for live captions

Wowza Streaming Engine
1

I’m using the latest Streaming Engine and need a way to customize M3U8 headers. As a quick example:

#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID=“subs”,NAME=“English”,FORCED=NO,AUTOSELECT=YES,URI=“subtitlelist_leng.m3u8”,LANGUAGE=“eng”

I want to update FORCED=NO to FORCED=YES. Is there support for this in 4.1.x?

2

Hi elcapitan26,

You can specify the FORCED attribute to have a value of “YES” by adding it in a SMIL file and using the SMIL file for your streaming. You can check the article on using WebVTT subtitles for HLS for more information on this.

Here’s a quick example:

<smil> 
<head> 
</head> 
<body> 
<switch>
<video src="mp4:sample.mp4" system-bitrate="500000"/>
<textstream src="mp4:sample.mp4" system-language="eng"> 
<param name="cupertinoTag" value="EXT-X-MEDIA" valuetype="data"/> 
<param name="cupertinoTag.TYPE" value="SUBTITLES" valuetype="data"/> 
<param name="cupertinoTag.LANGUAGE" value="en" valuetype="data"/> 
<param name="cupertinoTag.FORCED" value="YES" valuetype="data"/> 
<param name="cupertinoTag.NAME" value="English" valuetype="data"/> 
</switch> 
</body> 
</smil>

Michelle